The present invention relates to a waste water treatment method and a waste water treatment apparatus. The present invention relates to, as an example, a waste water treatment method and a waste water treatment apparatus in compliance with the total volume control of nitrogen in conformity to partial amendments to Water Pollution Control Law implemented as of April 2004 and in compliance with the emission reduction of toxic substances in conformity to PRTR (Pollutant Release and Transfer Register) Law implemented as of April 2001. The present invention relates to, for example, a waste water treatment method and a waste water treatment apparatus for treating two types of waste water, that is, waste water containing aminoethanol and dimethyl sulfoxide and waste water containing high concentration nitrogen (such as high concentration ammonium waste water, waste developer and dimethylformamide waste liquid) discharged mainly from semiconductor plants. Aminoethanol is designated as one of first-class designated chemicals in PRTR Law. The present invention also relates to, as an example, a waste water treatment apparatus and a waste water treatment method which can implement malodor treatment and microbial treatment without dilution, and therefore are excellent in initial costs, running costs and maintenance costs.
Conventionally, it has generally been regarded as impossible to apply microbial treatment to waste water which contains dimethyl sulfoxide and aminoethanol in a highly-concentrated form, specifically at about 3000 ppm for example, due to high microbial toxicity of aminoethanol.
In the case where microbial treatment has been applied to the waste water containing both aminoethanol and dimethyl sulfoxide, the microbial treatment has generally been applied thereto with the concentrations of aminoethanol and dimethyl sulfoxide are respectively as low as several hundred ppm.
Accordingly, the waste water containing high concentration aminoethanol and/or dimethyl sulfoxide at as high as 3000 ppm or more has been concentrated to about 1/10 with use of an evaporator as a physical method. Resultant concentrated solution has been disposed as industrial waste.
That is to say, the waste water is concentrated by using the evaporator and discharged as industrial waste from plants. In this way, the concentrated solution is deemed as industrial waste, and therefore, quantity of industrial waste from the plants is increased. In the disposal way of the concentrated solution as industrial waste, the concentrated solution has generally been disposed by incineration. Therefore, there have been problems such as air pollution because heavy oil or the like is used as fuel. Moreover, the treatment using the evaporator consumes a large amount of energy and involves large plant equipment, which leads to large initial, running and maintenance costs.
A biological treatment method is disclosed as a conventional art by JP 3467671. This biological treatment method is a nitrification and denitrification method wherein organic waste water in a raw water tank is fed to a denitrification tank and a nitrification tank sequentially by using liquid supply pumps while being circulated between both the tanks. Thereby, ammonia nitrogen contained in the organic waste water is reduced to nitrogen gas by biological nitrification and denitrification actions to be removed. Further, sludge and treated water are separated by means of a filtration membrane unit immersed in the waste water in the nitrification tank with use of a suction pump.
The feature of the nitrification and denitrification method is that part of organic waste water fed from the denitrification tank to the nitrification tank is ejected to the organic waste water in the denitrification tank, wherein a conduit pipe from the denitrification tank to the nitrification tank diverge in some midpoint, and an end of a diverged pipe is opened to the denitrification tank.
Another biological treatment method is disclosed in JP 3095620 as another conventional art. In this biological treatment method, a biological nitrogen removing apparatus is used. The biological nitrogen removing apparatus has a denitrification tank for receiving inflow of raw water containing organic substances, a nitrification tank for receiving inflow of denitrification tank mixtures from the denitrification tank, a nitrified liquid circulation channel for circulating nitrified liquid of the nitrification tank to the denitrification tank, and a nitrification tank diffuser placed inside the nitrification tank.
Specifically, the biological nitrogen removing apparatus has a denitrification tank, which is provided with a zone filled with denitrifying bacteria-immobilizing carriers, so as to catch and remove suspended solids in the raw water flowing into the denitrification tank. A raw water introduction channel and a nitrified liquid circulation channel are linked to a lower position of the zone filled with the denitrifying bacteria-immobilizing carriers in the denitrification tank. A sludge hopper section is provided on the bottom section of the denitrification tank so as to accumulate and remove the suspended solids caught in the zone filled with the denitrifying bacteria-immobilizing carriers. The sludge hopper section is provided with a hopper diffuser.
However, as stated above, microbial treatment has not conventionally been applied to the waste water containing high concentration aminoethanol and dimethyl sulfoxide at about 3000 ppm, in general, due to high biological toxicity. Therefore, the above-stated concentration method have been used for treating the waste water containing high concentration aminoethanol and dimethyl sulfoxide which cannot undergo microbial treatment due to high biological toxicity.
However, the concentration method has such problems as increase in energy consumption and increase in industrial waste as concentrated solution.
On the other hand, it has been demanded to efficiently treat malodor including sulfur generated during waste water treatment while reducing initial costs, running costs and maintenance costs.